U.S. patent number 6,355,320 [Application Number 09/410,728] was granted by the patent office on 2002-03-12 for synthetic closure and manufacturing process thereof.
This patent grant is currently assigned to Nomacorc, LLC. Invention is credited to Michael Allman, Eduardo Lauer.
United States Patent |
6,355,320 |
Allman , et al. |
March 12, 2002 |
Synthetic closure and manufacturing process thereof
Abstract
A plastic foamed synthetic closure for use with liquid bearing
containers which closely simulates natural cork products is
realized by incorporating color concentrates into the polymer melt
and forming the color concentrates into elongated streaks. The
desired emulation is further enhanced by arcuately pivoting the
foamed plastic material during the production to form curved or
sinusoidal-shaped streaks. This invention also provides
manufacturing methods for mass producing individual products in a
continuous motion casting system wherein fully complete products
are formed in polymer casting members, which receive foam material
exiting from the die and allow the foamed material to be formed in
a continuous operation in the casting members. Finally, the present
invention also teaches a unique system for maintaining and
delivering carbon dioxide in its supercritical phase for use as a
blowing agent.
Inventors: |
Allman; Michael (Wilson,
NC), Lauer; Eduardo (Zebulon, NC) |
Assignee: |
Nomacorc, LLC (Zebulon,
NC)
|
Family
ID: |
26802230 |
Appl.
No.: |
09/410,728 |
Filed: |
October 1, 1999 |
Current U.S.
Class: |
428/36.5;
215/355; 428/304.4; 428/317.9; 428/314.8; 215/358; 215/364;
428/195.1 |
Current CPC
Class: |
B29C
48/05 (20190201); B29C 48/303 (20190201); B65D
39/0011 (20130101); B65D 39/00 (20130101); Y10T
428/1376 (20150115); Y10T 428/249977 (20150401); Y10T
428/249953 (20150401); Y10T 428/249986 (20150401); B29C
48/03 (20190201); Y10T 428/24802 (20150115) |
Current International
Class: |
B65D
39/00 (20060101); B29D 022/00 (); B32B
003/26 () |
Field of
Search: |
;428/304.4,36.5,314.8,317.9,195 ;215/355,358,364 ;264/73,74,75 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Copenheaver; Blaine
Assistant Examiner: Vo; Hai
Attorney, Agent or Firm: Stoltz; Melvin I.
Parent Case Text
This application claims benefit of Provisional Application Ser. No.
60/105,073 filed Oct. 21, 1998.
Claims
What we claim as new and desire to secure by Letters Patent is:
1. A stopper or closure for a fluid product retaining container
constructed for being inserted and securely retained in a portal
forming neck of the container, said stopper/closure comprising:
A. an elongated, solid, cylindrically shaped member dimensioned for
insertion in the portal of the neck of the fluid product retaining
container for closing and sealing the fluid product in the
container;
B. said member being formed from extruded foamed plastic material
comprising a density ranging between about 100 kg/m.sup.3 to 500
kg/m.sup.3 and constructed for sealing the fluid product retained
in the container and preventing transfer of the fluid product from
the container prior to removal; and
C. said foamed plastic material comprises a blend of at least
formed two components, each comprising different hues or colors,
thereby imparting an integrally formed streaking effect to said
synthetic closure;
whereby a synthetic closure is attained which is capable of
completely sealing any desired fluid product in a container,
retaining the product in the container for any desired length of
time without any degradation of the fluid product or degradation of
the closure, while providing a visual appearance substantially
identical to a stopper formed from natural material.
2. The synthetic closure/stopper defined in claim 1, wherein the
cylindrically shaped member is further defined as comprising
substantially flat terminating surfaces forming the opposed ends of
said cylindrically shaped member.
3. The synthetic closure/stopper defined in claim 1, wherein the
plastic material forming the core member is further defined as
comprising medium density or low density, closed cell, foamed
plastic comprising one or more polymers selected from the group
consisting of plastic polymers, inert polymers, homopolymers,
copolymers, terpolymers, thermoplastic elastomers, and
thermoplastic olefins.
4. The synthetic closure/stopper defined in claim 3, wherein said
closed cell foam plastic material is further defined as comprising
at least one polymer selected from the group consisting of
polyethylenes, metallocene catalyst polyethylenes, polybutanes,
polybutylenes, polyurethanes, silicones, vinyl-based resins,
polyesters, ethylenic acrylic copolymers, ethylene-vinyl-acetate
copolymers, ethylene-methyl-acrylate copolymers,
ethylene-butyl-acrylate copolymers, ethylene-propylene-rubber,
styrene butadiene rubber, ethylene-ethyl-acrylic copolymers,
ionomers, polypropylenes, copolymers of polypropylene,
copolymerizable ethylenically unsaturated comonomers, and
thermoplastic amides.
5. The synthetic closure/stopper defined in claim 3, wherein said
closed cell, foamed plastic material is further defined as
comprising one or more polyethylenes selected from the group
consisting of high density, medium density, low density, linear low
density, ultra high density, and medium low density.
6. The synthetic closure/stopper defined in claim 5, wherein said
member further comprises a density ranging between about 200
kg/m.sup.3 to 350 kg/m.sup.3.
7. The synthetic closure/stopper defined in claim 1, wherein said
member is further defined as comprising
a. between about 10% and 60% by weight based upon the weight of the
entire member of at least one homopolymer,
b. between about 10% and 60% by weight based upon the weight of the
entire member of at least one thermoplastic elastomer, and
c. between about 10% and 60% by weight based upon the weight of the
entire member of at least one ionically cross-linked resin.
8. The synthetic closure/stopper defined in claim 7, wherein said
core member is further defined as comprising cell size ranging
between about 0.02 mm and 0.5 mm and a cell density ranging between
about 8,000,000 cells/cm.sup.3 to 25,000,000 cells/cm.sup.3.
9. The synthetic closure/stopper defined in claim 1 wherein said
member is further defined as being formed by extrusion.
10. The synthetic closure/stopper defined in claim 9, wherein said
extrusion process is further defined as incorporating one or more
blowing agents selected from the group consisting of carbon
dioxide, nitrogen, carbon, water, air nitrogen, helium, argon,
Azodicarbonamic Azodiisobutyro-Nitride, Benzenesulfonhydrazide,
4,4-Oxybenzene Sulfonylsemicarbazide, p-Toluene
Sulfonylsemi-carbazide, Barium Azodicarboxlyate,
N,N'-Dimethyl-N,N'-Dinitrosoterephthalamide, Trihydrazinotriazine,
Aliphatic Hydrocarbons having 1-9 carbon atoms, Halogenated
Aliphatic Hydrocarbons having 1-9 carbon atoms, Aliphatic alcohols
having 1-3 carbon atoms partially Hydrogenated Chlorocarbon and
Chlorofluorocarbons.
11. The synthetic closure/stopper defined in claim 10, wherein said
blowing agent is further defined as comprising between about 0.005%
and 10% by weight of the weight of the plastic material and
comprises an inert blowing agent selected from the group consisting
of nitrogen, carbon dioxide, water, air, nitrogen, helium, and
argon.
12. The synthetic closure/stopper defined in claim 9, wherein a
nucleating agent is employed in the extrusion process and said
nucleating agent is selected from the group consisting of calcium
silicate, talc, clay, titanium oxide, silica, barium sulfate,
diamatious earth, and mixtures of citric acid and sodium
bicarbonate.
13. The synthetic closure/stopper defined in claim 12, wherein said
nucleating agent is further defined as comprising between about 1%
and 10% by weight based upon the weight of the entire
composition.
14. The synthetic closure/stopper defined in claim 1, wherein the
outer surface of the member is further defined as comprising
indicia formed thereon.
15. The synthetic closure/stopper defined in claim 14, wherein said
indicia comprises one or more selected from the group consisting of
letters, symbols, colors, graphics, and wood tones.
16. The synthetic closure/stopper defined in claim 1, wherein said
foamed plastic material comprises at least a first component having
first hue and a second component having a second, different hue,
and each of said components having different viscosities and
different melt flow indicies.
17. The synthetic closure/stopper defined in claim 16, wherein the
melt flow index of the first component ranges between about 6 and
10, and the melt flow index of the second component ranges between
about 16 and 20.
Description
TECHNICAL FIELD
This invention relates to extruded elastomeric foams incorporating
extremely fine, uniform cell structures, constructed for employment
as a synthetic closure for liquid bearing vessels and, more
particularly, to a process for producing such products as well as
the product itself.
BACKGROUND OF THE INVENTION
For many years, the wine industry has relied on natural cork as the
sole product to seal wine bottles. However, there are several
negative aspects which are inherent in the use of natural cork as a
closure, all of which are disturbing to the industry and to
consumers.
One of the principal drawbacks of natural cork is cork taint. Cork
taint exists because of a chemical compound (2,4,6-trichloranisole
or TCA), which is found naturally in the cork bark. This taint
effects the odor and flavor of the wine and accounts for as much as
50% of the spoilage of all wine bottled with natural cork.
Another problem is broad diversity that exists for natural cork
quality. In an attempt to deal with this problem, the cork industry
has adopted standards which are subjective at best and generally
relate to the number of lenticels, cracks and their sizes, overall
aesthetics, smells and functionality, all of which are subject to
the growing and harvesting conditions experienced in the cork
growing regions of the world. Each individual cork is therefore
unique unto itself in all of its characteristics and possesses a
wide range of variations. These variations may cause as much as 20%
spoilage of bottled wine, due principally to such physical
characteristics as non-circular cross-sections, cork size, density,
and cell sizes internal to the natural cork that cannot be seen
during manual grading. These uncontrollable variations often cause
leakage and unwanted oxidation of the wine.
A further drawback of natural cork is the fact that cork is an
extremely limited resource. Natural cork bark is harvested from the
cork oak which is only able to replenish itself on the order of
once every 10 years. This, coupled with the fact that new plantings
require 30 years to come to maturity, leaves the natural cork
industry with limited ability to increase productivity to meet the
demand of an ever-increasing commodity.
A final drawback is the cost of natural cork. Due to its limited
availability, especially for higher quality products, and
increasing demand, the cost of using cork products in the wine
industry has seen a constant rise over the years. This trend
probably will not shift as it is a limited resource and is a very
labor intensive industry.
In spite of these difficulties and drawbacks, a majority of all
wine bottles utilize a natural cork for their closures. As a
result, both the wine industry and the consumers have accepted cork
closures and have tolerated a certain level of defective product.
As a result, efforts to develop a synthetic closure acceptable to
the wine industry and consumers have not materialized, except in
the area of screw caps, made from aluminum and plastic, and a small
segment of molded closures. However, in spite of the industry's
desire to eliminate the inherent problems found with cork closures,
prior to the present invention, no closure has been developed which
is (1) able to maintain the ceremony of opening the wine bottle,
(2) has none of the negative attributes of natural cork, (3) is
aesthetically acceptable, (4) meets all the physical requirements
of a high speed mass bottling, (5) is consistently reproducible,
(6) meets all regulatory criteria, and (7) is cost effective in a
mass production setting.
Therefore, it is a principal object of the present invention to
provide closure means for containers which is manufacturable from
synthetic materials and effectively closes and seals any desired
bottle, container, package and the like.
Another object of the present invention is to provide a synthetic
closure having the characteristic features described above which is
manufacturable on a continuing production basis, thus providing
lower manufacturing costs compared to natural closures and
satisfying industry requirements for a removable bottle stopper
which is producible substantially more economically than cork
closure/stoppers.
Another object of the present invention is to provide a synthetic
closure having the characteristic features described above which
meets or exceeds all of the requisite physical characteristics
found in natural closures or stoppers such as cork.
A further object of the present invention is to provide a synthetic
closure or stopper having the characteristic features described
above which is capable of simulating all of the visually aesthetic
and tactile characteristics found in natural stoppers, such as
cork, so as to be effectively a substitute for cork stoppers or
closures for the wine industry, particularly its ends users in both
appearance and feel.
Another object of the present invention is to provide a synthetic
closure or stopper having the characteristic features described
above which is capable of being employed in conventional bottling
equipment for being inserted into a bottle container without
experiencing any unwanted physical damage.
Another object of the present invention is to provide a synthetic
closure or stopper having the characteristic features described
above that can be substituted for a cork stopper in wine bottles,
providing all of the desirable characteristics of conventional cork
stoppers while also being removable from the bottle in the
conventional manner without breaking.
Another object of the present invention is to provide a synthetic
closure or stopper having the characteristic features described
above, which is physiologically neutral, capable of being
sterilized, as well as capable of being formed to visually simulate
any desired classification of natural cork.
A further object of the present invention is to provide a synthetic
closure or stopper having the characteristic features described
above which is odorless, remains odorless in position, is
tasteless, and only absorbs limited amounts of water.
Another object of the present invention is to provide a synthetic
closure or stopper having the characteristic features described
above which is unaffected by diluted acids and bases as well as
unaffected by most oils.
Another object of the present invention is to provide a synthetic
closure or stopper having the characteristic features described
above which does not shrink, does not age, does not absorb mold or
fungus, and resists damage from insects.
Another object of the present invention is to provide a synthetic
closure or stopper having the characteristic features described
above which can be mass produced on a continuing basis and
eliminates any spoilage of wine due to cork taint.
Other and more specific objects will in part be obvious and will in
part appear hereinafter.
SUMMARY OF THE INVENTION
By employing the present invention, all of the difficulties and
drawbacks found in the prior art have been eliminated and an
extruded synthetic closure capable of being manufactured
continuously and providing a low cost product is achieved. In
addition, the synthetic closure of the present invention possesses
all of the physical and desirable visual characteristics required
by the wine industry. As a result, the present invention achieves a
synthetic closure usable in the wine industry as a bottle closure
which is virtually equivalent in all respects to a natural cork
closure.
One of the principal requirements imposed upon a closure for wine
bottles is its sealing capability. In the wine industry, high speed
corking machines are employed which subject the closures to extreme
forces. These corking machines typically utilize a plurality of
compression jaws, typically ranging between two and four, which
radially compress the closure from its normal diameter to a
substantially smaller diameter, which is about one third of its
original size. Then, by employing a plunger or ram, the closure is
forced from the jaws in the compressed mode directly into the neck
of the bottle, wherein the closure is able to expand to its
original diameter, sealing the bottle.
As a result of the construction of the compression jaws, a knife
edge is created on each jaw member. Consequently, between two and
four separate locations incorporate an inherent knife edge formed
on the jaw element. These knife edges often crease or score the
outer surface of the closure, unless the closure is sufficiently
elastic in nature to be able to resist this scoring or creasing
action. In many instances, creasing or scoring of the closure
causes the bottle of wine to leak or allows the transfer of the
outside atmosphere into the bottle, causing oxidation of the wine
and rendering the wine unpalatable.
In the present invention, the formulation employed for attaining a
synthetic closure achieves a resulting product which is capable of
resisting the compressive forces imposed on the closure by the
corking jaws, as well as resisting any permanent scoring or
creasing of the outer surface. In addition, the synthetic closures
of the present invention also possess a high compression recovery
rate, enabling the synthetic closure of the present invention to
return to at least 960/o of its original diameter upon exiting the
jaws of the corking machines. In this way, the synthetic closure of
the present invention is capable of providing all of the desired
attributes for attaining a viable closure for the wine industry,
enabling the closure to be employed in normal production equipment
for completely sealing the wine bottle upon insertion therein.
Another feature of the present invention is the ability to attain a
synthetic closure which is capable of receiving and cooperating
with any desired surface treatment. In this way, the extraction
forces required to remove the synthetic closure of the present
invention from a wine bottle is easily controlled.
Extraction force is typically defined as the force a person of
ordinary strength must exert to remove the closure from the one
bottle without undue stress or strain. Typically, between about 40
pounds and 80 pounds of pulling force is required. In the present
invention, the synthetic closure defined herein is capable of
easily meeting this standard, due to the compatibility of the
formulation of the present invention with conventional surface
treatments. In addition, this compatibility also enables the
closure of the present invention to incorporate any other treatment
typically required for controlling insertion depth.
Another feature of the present invention is the attainment of a
synthetic closure which has a neutral smell or aroma and does not
impart any objectionable fragrance, smell or aroma to the wine
itself. In this way, the normal wine fragrance is not disturbed and
the flavor sensation associated with a particular vintage or type
of wine is not negatively impacted. Furthermore, the present
invention does not impact unwanted flavors to the wine, allowing
the wine to remain with all of its natural flavor.
In addition to attaining all of these physical attributes, the
formulation of the synthetic closure of the present invention also
needs or exceeds all requirements of the Food, Drug and Cosmetic
Act, enabling the closure to be used in direct contact with food
products. Furthermore, in accordance with the present invention,
unique color concentrates are capable of being integrated into the
formulation. In this way, the synthetic closure of the present
invention may be formulated with a visual appearance virtually
identical to natural cork. In this regard, the growth rings
typically associated with natural cork are able to be emulated by
the synthetic closure of the present invention. Furthermore, if
desired, any coloring can be imparted into the synthetic closure to
provide a unique visually distinctive product, as well as provide a
surface upon which any printed indicia, such as logos, dates,
characters, etc. can be applied to the surface of the synthetic
closure.
The invention accordingly comprises an article of manufacture
possessing the features, properties, and relation of elements which
will be exemplified in the article hereinafter described, as well
as the several steps in relationship of one of more steps with
respect to each of the other and producing the article of
manufacture defined herein, with the scope of the invention being
indicated in the claims.
THE DRAWINGS
For a fuller understanding of the nature and object of the
invention, reference should be had to the following detailed
description taken in connection with the accompanying drawings, in
which:
FIG. 1 is a cross-sectional side elevational view of a portion of
the linear flow extrusion device employed in the present
invention;
FIG. 2 is an enlarged cross-sectional side elevational view of the
extrusion die employed in the extrusion device of the present
invention;
FIG. 3 is a top plan view of the extrusion die of FIG. 2;
FIG. 4 is a diagrammatic side view depicting the extruded foam
product of the present invention exiting the extrusion die for
cooling and arcuate pivoting movement;
FIG. 5 is an end view of the pivot inducing systems employed and
shown in FIG. 4;
FIG. 6 is a diagrammatic view of a pumping system preferably
employed for delivering the blowing agent to the desired location
in the present invention;
FIG. 7 is a cross-sectional side elevation view depicting the
preferred construction of the blowing agent injector;
FIG. 8 is a diagrammatic top plan view of a continuous motion
casting system of the present invention for use in mass producing
completely finalized finished products;
FIG. 9 is a greatly enlarged top plan view of the polymer receiving
zone of the continuous motion casting system of FIG. 8;
FIG. 10 is a greatly enlarged top plan view of the product
discharge zone of the continuous motion casting system of FIG.
8;
FIG. 11 is a greatly enlarged top plan view of the polymer
receiving zone of the continuous motion casting system of FIG. 8
wherein a coextrusion die is employed;
FIG. 12 is a cross-sectional plan view of a plurality of polymer
casting forms of the continuous casting system of FIG. 8 depicted
in mating, cooperating engagement with each other;
FIG. 13 is a cross-sectional plan view of polymer casting forms
depicted in mating engagement; and
FIG. 14 is a cross-sectional side view of the mating polymer
casting forms of FIG. 13.
DESCRIPTION OF THE INVENTION
By employing the present invention, all of the drawbacks and
difficulties of the prior art are overcome and an extruded, medium
to high density, uniform, extremely fine cell elastomeric,
synthetic foam closure is achieved. In accordance with this
invention, a unique formulation and extrusion process is provided
which completely overcomes the inefficiencies of prior art attempts
to achieve a synthetic closure acceptable to both the industry and
consumers. By employing the teachings of the present invention, the
physical and visual attributes of natural cork are provided without
the negative aspects of natural cork products.
In order to achieve the advancement attained by the present
invention, a unique formulation is employed. By employing the
present invention, an extruded, uniform, extremely fine cell,
elastomeric foam closure is attained having a medium to high
density of between about 100 and 500 kg/m.sup.3. In order to attain
this result, the elastomeric foam closure comprises a blend of
plastic polymers, additives, color concentrates, and a combination
of physical and chemical blowing agents to produce a medium or low
density closed cell foam rod with all of the desired physical and
aesthetic attributes.
In the present invention, the preferred polymers are selected from
one or more groups of materials compatible with one another and
meeting FDA guidelines for direct food contact. These groups
include homopolymers, copolymers (including random copolymers,
alternating copolymers, block copolymers or grafted copolymers),
terpolymers, interpolymers, as well as a group of compounds known
to those skilled in the art as thermoplastic elastomers (TPE's) and
thermoplastic olefins (TPO's). These thermoplastics include
polyurethanes, elastomeric alloys, thermoplastic copolyesters,
styrene block copolymers (such as SEBS, SBS, styrene isoprene) and
thermoplastic amides.
The preferred combination of the present invention comprises a
polyethylene homopolymer, polyolefin elastomer and an ionically
cross-linked resin. It has been found that this blend, either
independently or in combination with all of the other components or
formulations of this invention, yields a foam structure capable of
meeting the demands of the wine industry.
One of the principal requirements that must be met by a synthetic
wine closure is the elastic recovery characteristics which will
enable the synthetic closure to withstand creasing and scoring from
the jaws of the high speed corking apparatus used in the wine
industry for mass bottling. In order to attain a high quality
synthetic closure in accordance with the present invention, the
preferred formulation comprises one or more homopolymers ranging
between about 10% and 60% of the entire composition. More
preferably, it has been found that the homopolymers should comprise
between about 20% and 40%, with 30% being optimum. Generally, the
percentage of thermoplastic elastomer employed in the composition
ranges between about 10% and 60%, preferably between about 20% and
40%, with 30% being optimum. Finally, the percentage of the
ionically cross-linked resin ranges between about 10% and 60%,
preferably between 20% and 40%, with 30% being optimum.
In accordance with the present invention, a synthetic bottle
closure is attained which possesses all of the physical
characteristics to enable the synthetic closure to be virtually
equivalent to the desirable characteristics of natural cork. In
addition, in order to provide a further enhancement to the present
invention, the preferred embodiment is constructed in a manner
which visually simulates the appearance of cork. As one aspect of
this construction, color concentrates are incorporated into the
synthetic cork formulation in a manner which emulates the visual
appearance produced by the "growth rings" typically found in cork
closures.
Preferably, the color concentrate utilized to obtain the desired
"growth ring effect" is a combination of two distinctly different
hues with each of these hues being achieved by using different
viscosity polymers as part of a pigmenting system which is
compatible with the other components of the synthetic closure. For
example, light brown and dark brown pigmenting polymers can be
employed, with the light brown polymers having a melt flow index of
between about 6 and 10, while the dark brown polymer have a melt
flow index of between about 16 and 20. This disparity in melt flow
indices and, hence the viscosity of the polymers, produces a
mottling effect within the extruder.
As shown in FIGS. 1-5, the system of the present invention employs
die head 20 which comprises linear flow extrusion device 22 and die
24. In addition, linear flow extrusion device 22 comprises
apertures or passageways 23 formed therein for controlling the flow
of the polymer melt therethrough.
As diagrammatically depicted in these figures, color concentrates
25 are incorporated into the plastic melt 26. Mottling
characteristics produced by the pigmented polymers or concentrates
25 are transformed into random linear stripings or strips 27, which
may have different widths as the color concentrates 25 and polymer
melt 26 pass through apertures 23 of linear flow extrusion device
22. By employing this construction, the growth rings of the natural
cork product are simulated.
In addition, as is more fully detailed below, the preferred process
of the present invention utilizes oscillating motion on the
downstream portion of the extrusion to continuously manipulate the
extruded foam rod in a slight back and forth motion, producing
slight "wiggles" or interruptions in the linearity of the streaks.
In this way, the "growth ring effect" is further emulated and
enhanced.
Other components incorporated into the composition of the present
invention comprises one or more suitable and compatible nucleation
agents.
Preferably, the nucleating agent is selected from the group
consisting of titanium oxide, silica, talc, calcium silicate,
barium sulfate, and diamatious earth. Although these compounds are
preferred, other agents known to those skilled in this art may also
be used.
Generally, the nucleating agent comprises between about 1% and 10%
by weight of the weight of the entire composition and, typically,
between about 2% and 8% by weight of the entire composition. In
addition, it has been found that 5% of the composition is
preferred.
Furthermore, a chemical blowing agent is also preferably employed
in the formulation of the foamed rod of the present invention.
Preferably, an endothermic alkali carbonate mixture is employed
which provides a multifunctional purpose as the chemical makeup and
particle size is advantageous in nucleating the foam even beyond
the capability of the nucleating agent. This intense nucleation
yields extremely fine cell size in combination with the extreme
atomization achieved by also employing a physical blowing agent.
Generally, the chemical blowing agent comprises between about 0.5%
and 5% by weight of the weight of the entire composition, with
between 1% and 30% being typically employed. However, in the
preferred composition, about 2% by weight is employed.
As mentioned above, a physical blowing agent is preferably employed
in addition to the chemical blowing agent. It has been found that
an effective physical blowing agent may be selected from the group
consisting of aliphatic hydrocarbons and inorganic blowing agents.
In regard to the use of aliphatic hydrocarbons as the physical
blowing agent, it is preferred to employ one or more agents
selected from the group consisting of methane, ethane, propane,
n-butane, isobutane, n-pentane, isopentane and neopentane. In
addition, the preferred inorganic blowing agent preferably
comprises one or more agents selected from the group consisting of
carbon dioxide, nitrogen, water, air, helium, and argon. The most
suitable of these blowing agents is liquid carbon dioxide in its
supercritical phase.
Generally, the physical blowing agent incorporated into the polymer
melt ranges between about 0.01% and 3% by weight based upon the
weight of the entire composition. In addition, it has been found
that between about 0.05% and 2% by weight is effective, with
between about 0.1% and 1% being preferred. These percentages will
generally produce densities, of the final extruded, extremely fine
cell elastomeric foam suitable for a synthetic wine closure on the
order of 100 to 500 kg/m.sup.3, typically on the order of between
150 to 300 kg/m.sup.3.
In addition to the blowing agents detailed above, other blowing
agents that may be employed comprise one or more selected from the
group consisting of nitrogen, carbon, water, air nitrogen, helium,
and argon, Azodicarbonamic Azodiisobutyro-Nitride,
Benzenesulfonhydrazide, 4,4-Oxybenzene Sulfonylsemicarbazide,
p-Toluene Sulfonylsemi-carbazide, Barium Azodicarboxlyate, N,N
'-Dimethyl-N,N '-Dinitrosoterephthalamide, Trihydrazinotriazine,
Aliphatic Hydrocarbons having 1-9 carbon atoms, Halogenated
Aliphatic Hydrocarbons having 1-9 carbon atoms, Aliphatic
Hydrocarbons having 1-9 carbon atoms, Aliphatic alcohols having 1-3
carbon atoms and partially Hydrogenated Chlorocarbon and
Chlorofluorocarbons.
The Process
The conventional technique of foaming is well known to those
skilled in the art. However, one aspect of the present invention
comprises a novel process which has been developed in order to
achieve the desired final product on a consistent, repeatable
production basis. In carrying out the process of the present
invention, an extruder is employed which comprises a tandem single
screw construction, typically a conventional single screw extruded.
However, preferably, a counter-rotating twin screw extruder is
employed utilizing screw designs that produce a high degree of
plastification in the first stage, without adding excess shear and
temperature into the melt.
In accordance with the present invention, the physical blowing
agent is injected between the first and second stage. In addition,
the second stage includes an aggressive dispersive as well as
distributive mixing section which achieves the proper solubility of
carbon dioxide in its supercritical phase within the polymer melt,
while maintaining the pressure requirements of carbon dioxide in
its supercritical phase.
Injecting carbon dioxide as a blowing agent requires a novel
pumping system to accurately and consistently deliver carbon
dioxide to the injector in its supercritical phase. In the
preferred embodiment, as diagrammitcally depicted in FIG. 6, the
delivery system comprises a dual cylinder syringe type pump 30
which incorporates a water cooled jacket. In addition, the carbon
dioxide is stored as a liquid in tank 31 and delivered to pump
system 30 through tubing 32, all of which are surrounded by water
cooled jackets 33.
In the preferred construction, pump system 30 is retrofitted with a
mass flow meter coupled to a feedback loop with appropriate
computer controls to maintain the flow volume to within 0.1 ml/hr.
The carbon dioxide flow from pump system 30 is carried in tubing
31, to a pre-pressure regulator 34, and then delivered to the
injectors of the extruder. All tubing 31 used to carry this carbon
dioxide is preferably surrounded by water cooled jackets 33. In
this way, constant pressure above the pre-pressure set point of
2600 psi is maintained.
In this embodiment, pre-pressure is regulated through a diaphragm
type valve with a variable set point. This regulator is constructed
so as to move a specific volume of carbon dioxide without the loss
of pressure on the outlet side. All components of the pumping
station utilize a novel cooling system which maintains carbon
dioxide at a temperature well below its critical temperature. This
construction allows for both the refilling and the pumping of
carbon dioxide at a known density and volume, with repeatability
when switching between pumping cylinders. The cooling medium
employed preferably comprises chilled water circulating at a
constant 20.degree. C., which maintains the carbon dioxide at
25.degree. C. Therefore, by maintaining a pressure of 2500 psi at
25.degree., a constant density of 0.906 gram/ml is achieved as well
as maintaining the carbon dioxide in its liquid phase.
In order to increase the solubility of the carbon dioxide Within
the polymer composition and achieve a resulting product having much
finer cell structure than can be achieved with conventional foaming
techniques, the temperature and pressure of the carbon dioxide must
be held well above its critical points at the injector. In
accordance with the present invention, the result is attained by
employing a uniquely constructed injector depicted in FIG. 7.
As shown in FIG. 7, injector 40 is insulated with a fiber
reinforced phenolic sleeve 41 which preferably extends between
about 60% and 100% of the injector length, from the barrel (heat
source) to the injection point. Preferably, injector 40 is held in
place by retaining bolt or collar 42. It has been found that the
construction of injector 40 is of paramount importance in
maintaining the liquid phase of the carbon dioxide just prior to
injection.
Carbon dioxide typically becomes supercritical in the final 25% to
35% of the injector length before entering the melt stream. At this
point, the back pressure within the extruder should be between
about 1700 psi and 2000 psi, in order to maintain cell size of the
final product between about 0.02 mm and 0.3 mm, with a cell density
ranging between about 25,000,000 cells/cm.sup.3 and 500,000
cells/cm.sup.3.
The third stage of the extruder is designed for pumping and cooling
of the polymer melt. The screw in this last stage is basically
constructed for advancing the product through the system.
Preferably, cross cuts are formed in the forward-mg blades,
oriented in such a manner as to force the polymer melt from the
lower areas within the melt pool at the root of the screw into
contact with the inner barrel wall, where a liquid cooling medium
is circulated through a shell encompassing the entire circumference
of said barrel. This last stage must also maintain the pressure
required (1700 psi to 2000 psi. at 104.degree. C.) in order for the
carbon dioxide to be maintained in its supercritical phase and
remain solubilized within the polymer melt.
The gas laden polymer melt with its combination of polymer blends,
nucleators, chemical blowing agents, and color concentrates now
must pass through a linear flow extrusion device 22 shown in FIGS.
1-3. By the nature of its design, taking into account polymer flow
characteristics, the linear flow extrusion device 22 directs the
polymer flow into multiple flow channels separating out portions of
mottled polymer 25, causing a unique random streaking effect. After
passing through the die and associated adapters, and manipulated
downstream, the random streaking effect provides the desired
aesthetic quality.
In the preferred construction, the linear flow extrusion device 22
has a dual function by serving as a back pressure promoter and
maintaining a specific pressure through rheological calculations
which give a specific hole size in the device versus a known
throughput of polymer.
In accordance with the present invention, the extrudate from the
extruder may be processed using a variety of alternate
constructions. As provided herein, two alternate, unique and highly
desirable processing systems are detailed. Although these alternate
constructions are defined in connection with the manufacture of
synthetic closures for liquid bearing containers, such as wine
bottles, both processes defined herein can be employed for numerous
alternate products. Consequently, this disclosure is provided for
exemplary purposes and not as a limitation of the present
invention.
In the preferred method, as shown in FIGS. 8-14, the extrudate is
conveyed away from the exit portal or the die head of the extruder,
which may be a conventional foaming die in the case of a total
cellular product or a co-extrusion tool in the case of a composite
structure, directly into "continuous motion casting apparatus" 60.
As depicted, continuous motion casting apparatus 60 comprises two
separate and independent continuous loops 61 and 62, each of which
comprise a plurality of interconnected polymer casting forms 63 and
64. In the preferred construction, loop 61 comprises a plurality of
polymer casting forms 63, each of which are identical to each other
and are interconnected on opposed sides to adjacent casting forms
63, thereby forming continuous closed loop 61.
Similarly, loop 62 comprises a plurality of polymer casting forms
64 which are identical to each other and are interconnected on both
sides thereof to adjacent casting forms 64 to form continuous
closed loop 62. In addition, each casting form 64 is a mirror image
of casting form 63 and is constructed for cooperative mating
engagement with casting form 63 to define a forming zone therewith
in which the desired product is controllably produced.
In the preferred construction, each loop 61 and 62 continuously
revolve about two capstans, spaced about ten feet. In addition,
loops 61 and 62 are positioned in juxtaposed, spaced, cooperating
relationship, assuring that each polymer casting form 63 precisely
matches and cooperatingly engages with one polymer casting form 64
to establish therebetween a product forming zone 66, as shown in
FIGS. 12, 13, and 14.
In the preferred construction, polymer casting forms 63 and 64
engage with each other in cooperating relationship with the exit
portal or die head in order to receive the foamed polymer extrudate
directly in cavity 66. Thereafter, the casting forms remain engaged
for the desired travel distance, and are separated, when desired,
to produce the fully formed product. Once separated, each polymer
casting form 63 and 64 continues to rotate in their respective
closed loops 61 and 62, until returning to the original position
for another cycle.
Each set of casting forms 63 and 64 removes from the die lips the
appropriate amount of extrudate on each retrieval. The shape
defined by zone 66 in the casting form 63 and 64 will, when
pressurized by the expansion of the foaming extrudate, yield the
formation of a fine cell elastomeric closure suitable for the
stoppering of a wine bottle or other liquid bearing product.
Preferably, casting forms 63 and 64 are machined and maintained in
alignment so that even with the pressure exerted by the expansion
of the foam extrudate, no parting line can be detected.
In the preferred construction, forms 63 and 64 are machined to
include a chamfer on both ends of the closure. In addition, a
unique series of parting or cutting tools are incorporated between
each adjacent assembly of casting forms and are constructed to cut
or separate adjacent closures in order to yield a perfectly sized
synthetic closure.
This desired result is preferably accomplished by advancing the
parting tools into association with cam means which moves the tool
through the extrudate, leaving within casting form 63 and 64 and
extruded fine cell elastomeric closure. By employing this
construction, the discharge end of continuous motion casting
apparatus 60 produces the finished closure in a continuous,
mass-produced operation, with each product being separated during
the cutting operation and expelled by the opening of casting forms
63 and 64.
In the preferred construction, casting forms 63 and 64 are cored
for the circulation of heat transfer fluids which, when utilized as
a cooling medium for the fine cell elastomeric foam will form a
high density layer of elastomeric foam. In this way, when desired,
an outer peripheral layer is effectively created on the surface of
the resulting product. By creating a higher density outer layer or
surface, a synthetic closure is produced with resists the creasing
effect of the corking machine jaws.
In an alternate construction, casting forms 63 and 64 may be
constructed for interconnection with a vacuum source. In this
regard, a vacuum can be applied through the use of minute machined
orifices or through the use of pores found in sintered metals which
could be utilized as the material of construction for casting forms
63 and 64. The application of vacuum further amplifies the intimate
contact between the extrudate and the casting forms to ensure equal
cooling around the periphery of the closure. This process ensures
that the resulting synthetic closure comprises the precisely
desired cylindrical shape and dimensions.
Furthermore, if desired, casting forms 63 and 64 may comprise
material of construction which is textured by way of an etching
process, creating minute peaks and valleys on the surface in
contact with the extrudate. This leads to a significant increase in
the retention of surface treatments, such as silicone, parrafins,
etc., while also imparting a more natural feel to the closure, such
as a rough texture, as opposed to a smooth texture, which is
extremely desirable in enhancing the uniqueness of the product and
process.
In an alternate method, depicted in FIGS. 4 and 5, the extrudate is
conveyed away from die 24 by way of a shaped or radiused belt
conveyor (not shown) which moves extruder, 28 which is formed as an
elongated continuous foamed rod, trough a regulated cooling tunnel
45. Tunnel 45 is maintained at a temperature of about 22.degree.
C., while regulating the speed of the product independently of the
final speed, in order to accommodate the shrinkage factor of the
foam as it cools and crystallizes. In order to hasten the extrudate
cooling process, a water bath is employed by forced ambient air and
then another water bath continuously used in succession. This
method is particularly useful in cooling medium to high density
foams (100 to 500 kg/m.sup.3) since such foams are extremely good
insulators. It has been found that cooling the extrudate rapidly,
followed by allowing heat internal to the foam to make its way to
the surface during the forced ambient air phase, and then repeating
to the rapid water cooling provides a substantially more efficient
system then conventional water cooling only.
In order to enhance the visual effect provided by incorporating
color concentrates 25 to produce elongated colored strips or
streaks 27, as detailed above, this embodiment of the present
invention incorporates at least one pivot inducing plate 46,
cooperatively associated with support plate 47.
In the construction depicted in FIGS. 4 and 5, pivot inducing plate
46 is connected by linking arm 48 to rotating disc 49. As a result
of this construction, the continuous rotation of disc 49 causes
plate 46 to continuously move in a side to side or back and forth
manner in a horizontal plane, as represented by arrow 50.
By advancing extrudate or elongated foamed rod 28 along support
plate 48, with movable plate 47 in controlling contact or
engagement therewith, the side to side movement of plate 46 causes
extrudate/rod 28 to arcuately pivot along its central axis. This
rolling, arcuate motion causes the generally continuous horizontal
streaks 27 formed in due 24 to be formed into arcuately curved,
sinusoidal patterns 27.
By creating curved or sinusoidal shaped streaks 27 in extrudate/rod
28, the finally produced, synthetic closure incorporates growth
rings which closely emulate or simulate the growth rings commonly
found in natural cork products. As a result, the synthetic closure
of the present invention is further enhanced and improved.
In the next step, the extrudate 28 is forwarded by means of a
shaped, belted, pulling device known to those skilled in the art In
the present invention, however, the pulling requires a precisely
controlled speed, which works in conjunction with a non-contact
method of measurement and control. This construction is required in
order to provide quality assurance and dimensional stability, since
the product diameter and roundness must be maintained within + or
-0.15 mm. These tight tolerances are absolutely essential in order
to predict and control extraction force and insertion level. In
addition, extraction/insertion treatment may be provided to assure
optimum results.
An extremely precise cutter capable of achieving length control in
the order of + or -0.2 mm (0.008") at line speeds approaching 2400
ft./hr is also essential. These tolerances must be maintained,
since variations in length can affect head space within the bottle,
which has a direct correlation to movement of the closure out of
the bottle and potential pressure build up as wine changed density
and/or volume with temperature. In addition, length variations may
also give the appearance of a low filled bottle and, therefore,
would be viewed as a negative by the consumer.
Secondary Processes
After the primary phase is completed, several additional steps may
be required in order to impart desirable physical characteristics
to the product which will be of assistance when used in high speed
corking systems commonly found in the cork industry. One such step
is the chamfering of the ends of the closure. If the bottling
equipment being employed is older or does not receive the
maintenance required to sustain the equipment in an excellent
condition, a chamfered end is desirable. In addition chamfering may
be desirable from a purely aesthetic point of view, as this
operation provides the closure with a finished visual
appearance.
If chamfered ends are desired, the formulation employed for the
closure must be capable of being cut or ground on both ends with
customized equipment. Generally, the chamfer comprises a width of
between about 0.5 to 1 mm, and is cut on an angle of about
45.degree.. However, if desired, a customized chamfer may also be
produced.
Treatment
Traditionally, natural corks have been treated with substances that
are intended to increase or decrease the co-efficient of friction
of the closure. As is well known, the closure must have the ability
of being inserted into the bottle with minimal force requirements
being imposed on the equipment. In this way, the life of the
equipment is increased and the amount of maintenance required on
the bottling lines is decreased.
In addition, the closure must remain securely retained within the
neck of the bottle until such time as the wine is opened. To
accomplish this goal with a synthetic closure, the elastomeric foam
must have the ability to retain the additives or substances
employed by the industry for this purpose and must be able to use
existing equipment and technology for the application of these
treatments.
Typically, the substances employed are paraffinic in nature to
increase the coefficient of friction and silicone based oils to
decrease the coefficient of friction for the reasons stated above.
It is possible, however, to incorporate these substances and use a
pressure gradient principle as well as to allow for the "blooming"
of these substances out of the polymers used to create the
elastomeric foam and onto the surface. Because of the many bottle
types and the varying types of corking apparatus used in the
industry, custom formulations with specific amounts of these
substances generally require the application to be accomplished
through the use of existing equipment and technology.
It will thus be seen that the objects set forth above, among those
made apparent from the preceding description, are efficiently
attained and, since certain changes may be made in the above
constructions without departing from the scope of the invention, it
is intended that all matter contained in the above description or
shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended
to cover all of the generic and specific features of the invention
herein described, and all statements of the scope of the invention
which, as a matter of language, might be said if all
therebetween.
* * * * *